Many computers utilize disk drives for data storage and retrieval, such as magnetic recording hard disk drives that utilize a head assembly for reading and/or writing data on a rotatable magnetic disk. In such systems, the head assembly is typically attached to an actuator arm by a head suspension assembly comprising a head suspension and an aerodynamically designed slider onto which a read/write head is provided. When the head is positioned over a spinning disk during usage, the head position is at least partially controlled by balancing a lift force that is caused by an air bearing generated by the spinning disk and acting upon the slider, and an opposite bias force of the head suspension. In operation, the slider and head are designed to “fly” over the spinning disk at precisely determined distances from the disk surface at speeds that can range from 3600 revolutions per minute to over 15,000 revolutions per minute.
Head suspensions generally include an elongated load beam with a gimbal flexure located at a distal end of the load beam, and a base plate or other mounting means at a proximal end of the load beam. The gimbal flexure includes spring or gimbal arms that support a platform or tongue to which the slider is mounted. During operation of such a disk drive, the gimbal arms permit the slider to pitch and roll about a load dimple or load point of the load beam, thereby allowing the slider to follow the surface of the disk as it rotates, even if the disk surface is warped, has an irregular topography, or the like. The gimbal flexure, including the gimbal arms and tongue, are thus designed to provide a flexible connection to allow the necessary pitch and roll of the slider relative to the rotating disk surface. In addition to the variations in the disk surface, other operational and manufacturing considerations within the assembly itself can cause undesirable pitch and roll. For example, misalignment of components within the assembly can cause torque to be placed on the slider, which can induce the type of pitch and roll that can change the critical spacing between the slider and the disk surface.
Other head suspension assembly considerations are also important for proper alignment and performance of the various components. One other such consideration is the angular orientation of the tongue to which the slider is attached relative to the disk surface, which is also referred to as the “static attitude”. If the static attitude is not held to precise tolerances, torque may be imparted to the slider, which can also create undesirable pitch and roll of the slider relative to the disk surface.
In order to provide control of the critical spacing between the slider and disk surface, the pitch and roll stiffnesses of the gimbal flexure should be relatively low, which results in generally undesirable low vertical stiffness. In cases where the gimbal flexure has a low vertical stiffness, the mass of an attached slider can be significant enough to cause the gimbal tongue to separate from the load beam by a distance that causes permanent deformation or damage to the gimbal flexure structure. This damage is particularly likely when shock loads are imparted to the head suspension during its manufacturing processes and/or operation within a disk drive. To protect the fragile gimbal flexure structure from such damage, the head suspension may be provided with a limiter that, when engaged, can limit movement of the slider relative to the load beam, but still allows for low pitch and roll stiffnesses.
Various limiter features have been developed for use in head suspension assemblies, particularly in the gimbal region of such assemblies. For example, in the traditional Watrous-style gimbals known in the art, various limiter features have been used which limit the motion of the gimbal tongue and prevent large linear and rotary deflections of the gimbal tongue and the attached slider, particularly during shock events. In other words, the features of the limiter may serve the purpose of “engaging” during shock events to limit certain types of movement. A head suspension assembly may be subjected to such shock during assembly, testing, and/or shipping, for example, which can cause components of the assembly to become undesirably deformed or displaced relative to each other. Other shock events may occur when the suspension is part of a personal computer disk drive that is dropped or otherwise subjected to a sudden impact load that can cause the components of the suspension to displace relative to each other and relative to a disk surface. In these cases, a limiter can serve the purpose of preventing undesirable displacement of the gimbal tongue and slider components away from the load beam.
Previous versions of limiters involved forming a limiter prior to welding the various suspension components together. In these situations, a complex weaving motion was needed to properly position the tongue or gimbal component so that it could later be “caught” during shock events. This disadvantage was overcome with the use of components that allowed for welding prior to forming the limiters, which facilitated the automation of welding. Specifically, suspension components could be aligned or positioned relative to each other immediately prior to welding the components together.
Details regarding an integral flexible circuit suspension assembly and a polymeric ring gimbal which achieves very low pitch and roll stiffnesses without sacrificing high vertical and lateral stiffness can be found in commonly owned U.S. Pat. No. 6,515,832 to Girard, titled “Gimbal Stiffness Control for Head Suspension Assemblies”, the entire disclosure of which is incorporated herein by reference. The various features of this ring gimbal allow for setting nominal static angles while maintaining static angle positions throughout temperature and humidity changes. However, at extremely high G forces, it is possible that this gimbal may be damaged or distorted. Thus, it would be advantageous to optionally add a limiter to a polymeric ring gimbal of this type for certain applications or to add a limiter to other gimbal flexures that could utilize an additional protection feature. It would further be advantageous that this limiter could be added without requiring any weaving of components during assembly of the suspension and without having to form the limiter after welding.